1. Field of the Invention
The present invention generally relates to a wrapping film that can tightly wrap a cassette case or the like in which a tape cassette for a video tape recorder or audio tape recorder is accommodated and, more particularly, to a wrapping film that the user can open with ease.
2. Description of the Prior Art
It is customary that cassette cases are wrapped by wrapping films and then shipped so that the cassette cases may be protected from being damaged when transported or displayed on the show window or that the cassette cases may be improved in appearance (design). In the prior art, a cassette case is wrapped by a wrapping film as follows.
As shown in FIG. 1 of the accompanying drawings, a wrapping film 21 made of a polypropylene (PP) is provided in a roll shape and cut to have a predetermined length a. Then, as shown in FIG. 2, a cassette case is wrapped by the wrapping film 21 and partly overlapping portions are bonded (i.e., heat-sealed) to hold the cassette case in a sealed condition. As illustrated, there are provided a center sealing surface 22 and a side sealing surface 23, respectively. End edge portions of the center sealing surface 22 and the side sealing surface 23 are served as sealing areas 22a, 23a, respectively. While it is customary that the wrapping film 21 is wholly printed in color, the sealing areas 22a, 23a are not applied with inks. Accordingly, when the sealing areas 22a, 23a are heated under the condition that the cassette case is wrapped by the wrapping film 21, the wrapping film 21 made of polypropylene is melt-bonded to heat-seal the wrapping film 21.
The product in which the cassette case is wrapped by the polypropylene wrapping film 21 and tightly sealed by the heat-seal has a V-shaped notch 24 formed at one portion of the bonding portion on the center sealing surface 22 as shown in FIG. 2. The user can catch the notch 24 with a fingernail to tear the wrapping film 21 from the product.
FIGS. 3A and 3B show another example of the conventional wrapping film 21 having a so-called tearing strip 25 extended along the inner periphery of the wrapping film 21. The tearing strip 25 is interposed between the cassette case and the wrapping film 21 and wound around the outer periphery of the cassette case. One end of the tearing strip 25 is projected from the wrapping film winding end as a tab portion. The wrapping film 21 has slits formed at both sides of the tearing strip 25 so that the user can tear the wrapping film 21 along the tearing strip 25. Therefore, the user can hold the tab portion and tear the wrapping film 21 along the slits to open the wrapped film 21.
In the former wrapping film 21 having the V-shaped notch 24 formed at the bonding portion on the center sealing surface 22, the bonding portion has a large bonding strength so that the user cannot tear the wrapping film 21 from the center sealing surface 22 with ease. Thus, it is cumbersome for the user to open the wrapping film 21.
The latter wrapping film 21 having the tearing strip 25 also cannot avoid the following disadvantage. That is, if the user tears the wrapping film 21 along only the tearing strip 25 as shown in FIG. 3B, then the user cannot substantially tear the remaining wrapping film 21 even with a fingernail. Therefore, the wrapping film 21 is very difficult to be opened.
The tearing strip 25 is made of a material whose tear propagation resistance is higher than that of the wrapping film 21, By way of example, the tearing strip 25 is formed by bonding two kinds of transparent plastic films. When the tearing strip 25 is formed as a color tearing strip, the surface of one film material is printed and then bonded to the other film material.
The cassette case as a wrapped product is wrapped by the wrapping film made of the aforesaid material when the two films are melt-bonded to each other by the heat treatment of the wrapping film. However, since the surface of the cassette case is tightly wrapped by the wrapping film by heating the wrapping film at temperature higher than necessary in order to improve the appearance of the cassette case after the cassette case was packaged, the tab portion of the tearing strip also is bonded to the melt-bonded portion of the wrapping film. There are then the problems that the user cannot find the tab portion of the tearing strip without difficulty and that the user cannot tear the tab portion without difficulty. Particularly, when the user wants to supplement tapes in order to record sound or picture in a hurry, the user cannot open the wrapping film readily. There is then the problem that the user misses the opportunity to effect such recording.